This invention relates to linear bearing apparatus for use in moving an object along a rectilinear path with a minimum of friction. More specifically the invention pertains to the combination of a linear bearing assembly and a pair of opposed guide rails therefor, with the linear bearing assembly being of the type incorporating groups of recirculating antifriction balls. The recirculating-ball linear bearing apparatus in accordance with the invention finds particular utility in conjunction with industrial robots to be moved back and forth along rectilinear paths, among other applications.
Industrial robots are finding ever-increasing acceptance in various industries. They can not only increase productivity but also perform, with consistency beyond the physical capabilities of man, tasks that are too burdensome, monotonous, or dangerous for human operators. Among the functions commonly assigned to robots are: (1) the unloading of die-casting machines, quenching and delivering the castings to trim presses; (2) the welding of automobile frame parts; (3) the operating of forging presses; and (4) the loading and unloading of chucking machines. In some such functions the robots, or their articulated arms and hands, are required to travel back and forth along rectilinear paths. Linear bearings have been used for such travel of the robot arms because they can reduce frictional resistance to a minimum.
The current trend in robotized plants is toward higher productivity through an increase in the speed of the linear travel of the robot arms as they perform such functions as machine loading and unloading, and transferring and positioning of parts. Besides traveling at high speed, with frequent starts and stops, the robot arms as well as their hand assemblies make various degrees of free movement designed into them. Consequently the linear bearings carrying the robot arms must withstand the load acting thereon in every possible direction while allowing their frictionless linear movement.